Ferrous alloy



Oct. 16, 1928. Y 1,687,486

, F. A. ARMSTRONG FERRoUs ALLOY Filed Aug. 14, 1925 A V L25 t v b .50

INVENTOR /QHf/Ws/v/"Ony ATTORNEY Patented Oct. 16, 1928.

UNITED STATES 1,687,466 1 PATiizN'r OFFICE.

PERCY A.. E. ARMSTRONG, OF NEW YORK, N. Y.l

Emmons ALLOY.

Application filed .August 14, 1925. Serial No. 50,255.

My invention relates to ferrous alloys that have their-principal use as heat resisting parts which are required to resist progressive scaling at high temperatures, coupled with'great 5 strength at high temperatures, yet can be readily worked, machined and forged or cast into convenient' shapes., Their principal applications are for valves and valve parts for internal combustion engines andffor superheated steam, cast parts for anneallng boxes, carburizing containers, mixing.l paddles, either forged or cast, for the alkali industry, vand blades and rotors for gas turbines and boosters.

greater is the resistance to rust formation or surface discoloration. These properties, however,l are not of 'major importance as respects my present invention, which is pri-1 marilyintended for'those applications where heat is encounteredsuicient to discolor' the effective workingpart of the surface.

For automobile engine valves I prefer the carbon about .20% to .60%; for containers,

where hardness arising from high carbon is essential, carbon about 1% to 1.10%. :Steam valves subjected to high pressure and high temperature are preferably made with high carbon, such "as given above for valves for -internal combustion engines. Such high carf,

bon can be used toparticularly good advantage when the chromium is 4carried to the p high side of my limit. Y

.The silicon content adds materially to the scale resisting property of the alloy, as for example, thetemperature at-which an alloy steel containing carbon .25%, chromium 1.5%, silicon .25%, materially scales is about 1300 degrees F. If 4% silicon is added the y alloy contains essentially iron, chro-A low carbon .under .20%'; for those purposes scaling point temperature -is about 1700 degrees F.

Chromium also raises the scale .resisting temperature point. For instance, a steel containing carbon .45%, chromium 17%, silicon .25% will scale materially at aboutl1600 degrees F. if 2% of silicon is added the temperature at which material scaling is encountered is about 1750 degrees F.

Tantalum raises the scale resisting point. For example, 2% Aof tant'alum will raise the temperature for material scaling by about to 100 degrees F.

Tantalum` 4has an important property, whichv is lacking in additions of either chromium or silicon, or both, namely, tantalum 'f increases the strength of the alloy when heated to high temperatures.

-For example, the following table gives the approximate loads per square inch and tema peratures at which test -specimens of various compositions will break on a tensile testing machine. C C

Alloy A; .5 0 o r 9% Anoy A'; Aug/5,1 A tantalum.

4Alloy B: C .35%, Cr 12%, Si .3%.

Alloy B'.: o '35%, Cr 12%, si .35%,

Auoy C: C .40%, or 3.25%, `Si 3.60%.

Cr 3.40%, Si 3.50%,

Alloy C: .C .42%, TiAity' D o o loy 17 r 1,87 Si .507' Ta 27. Alloy E: o 1.691%@ 1'i5o%, si46%. o Alloy E Alloy E with 8% of Ta.

Si 3.50%. with 1 also 3% of Alloy 12.00 F. 1400" F. 1550 F. 1650 F.

Pounds sass:

The temperatures given above are approximate, and as each comparison was pulled underlsimilar conditions, the above figures can be taken as a rough guide as to the added strength imparted by the addition of tantalum. Tantalum is preferably from .25% to 3%, and morepreferably from 1% to 3%.

The full range of .chromium lcan be employed. I prefer to have the chromium content above .3%, and it should be above 7 if it is to be subjected to severe heat conditions. For general valve purposes 8% to 9% of chrolnium is usually suliicient. If rust resisting conditions are encountered, the chromium content should preferably be above 7%, and may advantageously be between 12% and 17%.

The silicon content is important to the alloy when subjected to heat, and I prefer to use 4% of silicon with loiv chromium, and about 1% ol silicon with high chromium.

Valves for internal combustion engines give good results made from the following compositions c. .45%, Cr snoei., Ta 3%. si 3259/.;

01%,01- 12.50%, Tn 6%, si

C .40%, Cr 4%, Ta 2%, Si

Internal combustion engine valves made i of ferrous alloys substantially as described do not scale at high temperatures, run well and smoothly in the guides and may be hardened to resist Wear on their tappct ends, making the alloywell suited for the production of in tegral or one-piece valves.

High melting point elements can be used, such as tungsten, molybdenum, columbium, vanadium, zirconium, titanium, cobalt, nickel. Nickel generally adds to the strength of the material at 1400 degrees F. and upwards, but makes the material hot short at around 2200 degrees F. It also does not add to the strength of the alloy ai', atmospheric temperatures. Nickel is preferred low.

The high melting point metals are desired o under 5%. They can, however, be used in part for the tantalum, particularly tungsten, molybdenum and columbium.

My alloy is, of course, resistant to saltA Water and hot Water atmospheres, to nitric acid, and dilute acids, such as citric, acetic, malic, particularly when the chromium content is increased and the carbon is decreased.

My alloy7 can be readily hardened if the carbon content is raised toward the upper limit, the higher the chromium, the more the carbon required to impart hardness by heat treatment. About 1900 degrees F. will generally be sufficient temperature, coupled with quenching,- to produce hardness. Annealing is advantageously done at about 1500 to 1750 degrees F.

My alloy generally contains manganese, preferably below 1.5%, and generallyunder .160% phosphorus and sulfur should be kept I claim:

1. Ferrous alloy resistant to fluids at elevated temperatures containing ap roximately ,chromium 9%, carbon .50%, si icon 3.5%, tantalum 3%, and the principal part of the remainder iron.

2. Valves for internal colnbustion engines made from a ferrous alloy containing approximately carbon .45%, chromium 8.5%, tantalum 3%, silicon 3.25%, and the principal part of the remainder iron.

3. Ferrous alloy resistant to rust, heat and acid, containing chromium 3%-18%, carbon .35%-1.1%, silicon 4%-1%, tantalum 29E-8%, and the principal part of the remainder iron.

4. Valve for internal combustion engines made from ferrous alloy containing carbon .4%-1%, chromium 4%-12.5%, silicon Ll%-2%, tantalum 2%-6%, and .the principal part of the remainder iron.

5. Ferrous alloy of high strength and resistance to scaling at high temperatures containing chromium about 1%20%, silicon about 4%-,1%, carbon from enough to produce material hardening up to about 1.25%, tantalum about .25%-3%, and the principal part of the remainder iron.

6. Valves for internal combustion engines of alloy according to claim 5.

7. Ferrous alloy of high strength and resistance to scaling at high temperatures containing chromium about 3%-10%, silicon about 4%-1%, carbon about .30%-1%, tantalum about 1%-3%, and the principal part of the remainder iron.

8. One-piece valves for internal combustion engines of alloy according to claim 7.

In testimony whereof, I have 'signed my name hereto.

PERCY A. E. ARMSTRONG. 

